Following discussion in the main PR thread, this adds language emphasizing protocol stewardship responsibilities alongside technical excellence.

Changes:

• Role Definitions table: Updated Maintainer and Core Maintainer summaries to reflect governance and protocol dimensions
• Maintainer responsibilities: Added ecosystem engagement and proposal refinement expectations
• Core Maintainer responsibilities: Added emphasis on restraint and sustainability in protocol evolution
• Reviewer/Maintainer requirements: Added expectation of foundational understanding of AI/model integration*

These are suggestions for consideration - happy for any of these to be modified, combined, or set aside based on what fits the overall vision for the SEP. They are meant as an articulation of the type of tweaks I envisioned.

• (I know I didn't mention this in the main PR thread, but I thought I might as well now that I was making suggestions anyway)